1. Field of the Invention
The present invention is generally directed to a method of regulating the liquid onium poly(hydrogen fluoride) composition utilized in a hydrogen fluoride catalyzed alkylation reaction.
2. Background
The catalytic alkylation of an isoparaffin with an olefin to produce a branched paraffin is a commercially important process for producing high octane gasoline. In general, the process comprises the reaction of an isoparaffin such as isobutane with an olefin such as propylene, 1-butene, 2-butene or mixtures thereof in the presence of a liquid acid alkylation catalyst in a reaction zone. Reaction is followed by separation of the product and unreacted hydrocarbons from the liquid alkylation catalyst in a settling zone and purification of the alkylate product. If the isoparaffin is isobutane and the olefin is a butene, the alkylate product is isooctane. Alkylate product is used to enhance the octane number of automotive gasoline and aviation gasoline.
Strong mineral acids are particularly effective catalysts for this alkylation process. Anhydrous sulfuric and anhydrous hydrofluoric acid (hereafter, HF) are examples of two commonly used acid catalysts. Though effective, the volatility and destructive effect of super-heated, pressurized mineral acids on animal and human tissue are well known. In another study it was shown that a release of HF from an alkylation reactor would form a dense aerosol cloud that could travel several kilometers downwind and only slowly disperses.
One method of mitigating the potential danger of an accidental release of HF has been the development of containment systems that spray water or aqueous neutralizing agent upon the detection of a reactor leak. Such systems rely on detection technology and/or plant personnel to determine if a hazardous condition exists before activation of the spray system.
Another method of mitigating the potential danger of accidental release of HF is the proposed use of HF containing compositions in the HF alkylation reaction that lower the volatility of HF. One such method is disclosed in U.S. Pat. No. 5,073,674 to G. A. Olah in which liquid onium poly(hydrogen fluoride) complexes are suggested as being useful. One skilled in the art, however, should appreciate that actual practice of such a system will require a balance of chemical reactants, reaction conditions and environmental conditions in order to achieve a commercially viable sustained reaction process.